Find/detect for first match in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Find the first even number in an array

What is the output of this Ruby code that finds the first even number in the array?

Ruby

numbers = [1, 3, 5, 8, 10]
result = numbers.find { |n| n.even? }
puts result

A nil

B 10

C 8

D 1

💡 Hint

Remember, find returns the first element matching the condition.

The method find returns the first element for which the block returns true. Here, 8 is the first even number.

❓ Predict Output

intermediate

Detect the first string longer than 4 characters

What does this Ruby code print when detecting the first string longer than 4 characters?

Ruby

words = ['cat', 'dog', 'horse', 'elephant']
result = words.detect { |w| w.length > 4 }
puts result

A horse

B dog

C elephant

D nil

💡 Hint

Check the length of each word in order.

The first word longer than 4 characters is 'horse'.

❓ Predict Output

advanced

Find first hash with value greater than 10

What is the output of this Ruby code that finds the first hash with a value greater than 10?

Ruby

items = [{a: 5}, {b: 15}, {c: 8}]
result = items.find { |h| h.values.first > 10 }
puts result

A {:a=>5}

B {:c=>8}

C nil

D {:b=>15}

💡 Hint

Look at the values inside each hash.

The first hash with a value greater than 10 is {:b=>15}.

❓ Predict Output

advanced

Detect first number divisible by 7

What does this Ruby code output when detecting the first number divisible by 7?

Ruby

nums = [10, 14, 21, 28]
result = nums.detect { |n| n % 7 == 0 }
puts result

A 21

B 14

C 28

D 10

💡 Hint

Check each number in order for divisibility by 7.

14 is the first number divisible by 7 in the array.

🧠 Conceptual

expert

Understanding find vs detect in Ruby

Which statement is true about the Ruby methods find and detect?

A <code>find</code> and <code>detect</code> are aliases and behave identically.

B <code>find</code> returns the first match, <code>detect</code> returns all matches.

C <code>find</code> only works on arrays, <code>detect</code> only on hashes.

D <code>detect</code> is deprecated and should not be used.

💡 Hint

Check Ruby documentation for these methods.

In Ruby, find and detect are exactly the same method with two names.